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Subject[PATCH v2 4/5] clocksource: add driver for i.MX EPIT timer
Date
From: Colin Didier <colin.didier@devialet.com>

Add driver for NXP's EPIT timer used in i.MX 6 family of SoC.

Signed-off-by: Colin Didier <colin.didier@devialet.com>
Signed-off-by: Clément Peron <clement.peron@devialet.com>
---
drivers/clocksource/Kconfig | 12 ++
drivers/clocksource/Makefile | 1 +
drivers/clocksource/timer-imx-epit.c | 273 +++++++++++++++++++++++++++
3 files changed, 286 insertions(+)
create mode 100644 drivers/clocksource/timer-imx-epit.c

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 8e8a09755d10..920a0874f3a4 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -576,6 +576,18 @@ config H8300_TPU
This enables the clocksource for the H8300 platform with the
H8S2678 cpu.

+config CLKSRC_IMX_EPIT
+ bool "Clocksource using i.MX EPIT"
+ depends on ARM && CLKDEV_LOOKUP && OF && (ARCH_MXC || COMPILE_TEST)
+ select TIMER_OF
+ select CLKSRC_MMIO
+ help
+ This enables EPIT support available on some i.MX platforms.
+ Normally you don't have a reason to do so as the EPIT has
+ the same features and uses the same clocks as the GPT.
+ Anyway, on some systems the GPT may be in use for other
+ purposes.
+
config CLKSRC_IMX_GPT
bool "Clocksource using i.MX GPT" if COMPILE_TEST
depends on ARM && CLKDEV_LOOKUP
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 00caf37e52f9..d9426f69ec69 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -69,6 +69,7 @@ obj-$(CONFIG_INTEGRATOR_AP_TIMER) += timer-integrator-ap.o
obj-$(CONFIG_CLKSRC_VERSATILE) += versatile.o
obj-$(CONFIG_CLKSRC_MIPS_GIC) += mips-gic-timer.o
obj-$(CONFIG_CLKSRC_TANGO_XTAL) += tango_xtal.o
+obj-$(CONFIG_CLKSRC_IMX_EPIT) += timer-imx-epit.o
obj-$(CONFIG_CLKSRC_IMX_GPT) += timer-imx-gpt.o
obj-$(CONFIG_CLKSRC_IMX_TPM) += timer-imx-tpm.o
obj-$(CONFIG_ASM9260_TIMER) += asm9260_timer.o
diff --git a/drivers/clocksource/timer-imx-epit.c b/drivers/clocksource/timer-imx-epit.c
new file mode 100644
index 000000000000..3530263eb35e
--- /dev/null
+++ b/drivers/clocksource/timer-imx-epit.c
@@ -0,0 +1,273 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * i.MX EPIT Timer
+ *
+ * Copyright (C) 2010 Sascha Hauer <s.hauer@pengutronix.de>
+ * Copyright (C) 2018 Colin Didier <colin.didier@devialet.com>
+ * Copyright (C) 2018 Clément Péron <clement.peron@devialet.com>
+ */
+
+#include <linux/clk.h>
+#include <linux/clockchips.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/of.h>
+#include <linux/sched_clock.h>
+#include <linux/slab.h>
+
+#define EPITCR 0x00
+#define EPITSR 0x04
+#define EPITLR 0x08
+#define EPITCMPR 0x0c
+#define EPITCNR 0x10
+
+#define EPITCR_EN BIT(0)
+#define EPITCR_ENMOD BIT(1)
+#define EPITCR_OCIEN BIT(2)
+#define EPITCR_RLD BIT(3)
+#define EPITCR_PRESC(x) (((x) & 0xfff) << 4)
+#define EPITCR_SWR BIT(16)
+#define EPITCR_IOVW BIT(17)
+#define EPITCR_DBGEN BIT(18)
+#define EPITCR_WAITEN BIT(19)
+#define EPITCR_RES BIT(20)
+#define EPITCR_STOPEN BIT(21)
+#define EPITCR_OM_DISCON (0 << 22)
+#define EPITCR_OM_TOGGLE (1 << 22)
+#define EPITCR_OM_CLEAR (2 << 22)
+#define EPITCR_OM_SET (3 << 22)
+#define EPITCR_CLKSRC_OFF (0 << 24)
+#define EPITCR_CLKSRC_PERIPHERAL (1 << 24)
+#define EPITCR_CLKSRC_REF_HIGH (2 << 24)
+#define EPITCR_CLKSRC_REF_LOW (3 << 24)
+
+#define EPITSR_OCIF BIT(0)
+
+struct epit_timer {
+ void __iomem *base;
+ int irq;
+ struct clk *clk_per;
+ struct clock_event_device ced;
+ struct irqaction act;
+};
+
+static void __iomem *sched_clock_reg;
+
+static inline struct epit_timer *to_epit_timer(struct clock_event_device *ced)
+{
+ return container_of(ced, struct epit_timer, ced);
+}
+
+static inline void epit_irq_disable(struct epit_timer *epittm)
+{
+ u32 val;
+
+ val = readl_relaxed(epittm->base + EPITCR);
+ writel_relaxed(val & ~EPITCR_OCIEN, epittm->base + EPITCR);
+}
+
+static inline void epit_irq_enable(struct epit_timer *epittm)
+{
+ u32 val;
+
+ val = readl_relaxed(epittm->base + EPITCR);
+ writel_relaxed(val | EPITCR_OCIEN, epittm->base + EPITCR);
+}
+
+static void epit_irq_acknowledge(struct epit_timer *epittm)
+{
+ writel_relaxed(EPITSR_OCIF, epittm->base + EPITSR);
+}
+
+static u64 notrace epit_read_sched_clock(void)
+{
+ return ~readl_relaxed(sched_clock_reg);
+}
+
+static int __init epit_clocksource_init(struct epit_timer *epittm)
+{
+ unsigned int c = clk_get_rate(epittm->clk_per);
+
+ sched_clock_reg = epittm->base + EPITCNR;
+ sched_clock_register(epit_read_sched_clock, 32, c);
+
+ return clocksource_mmio_init(epittm->base + EPITCNR, "epit", c, 200, 32,
+ clocksource_mmio_readl_down);
+}
+
+static int epit_set_next_event(unsigned long cycles,
+ struct clock_event_device *ced)
+{
+ struct epit_timer *epittm = to_epit_timer(ced);
+ unsigned long tcmp;
+
+ tcmp = readl_relaxed(epittm->base + EPITCNR) - cycles;
+ writel_relaxed(tcmp, epittm->base + EPITCMPR);
+
+ return 0;
+}
+
+/* Left event sources disabled, no more interrupts appear */
+static int epit_shutdown(struct clock_event_device *ced)
+{
+ struct epit_timer *epittm = to_epit_timer(ced);
+ unsigned long flags;
+
+ /*
+ * The timer interrupt generation is disabled at least
+ * for enough time to call epit_set_next_event()
+ */
+ local_irq_save(flags);
+
+ /* Disable interrupt in EPIT module */
+ epit_irq_disable(epittm);
+
+ /* Clear pending interrupt */
+ epit_irq_acknowledge(epittm);
+
+ local_irq_restore(flags);
+
+ return 0;
+}
+
+static int epit_set_oneshot(struct clock_event_device *ced)
+{
+ struct epit_timer *epittm = to_epit_timer(ced);
+ unsigned long flags;
+
+ /*
+ * The timer interrupt generation is disabled at least
+ * for enough time to call epit_set_next_event()
+ */
+ local_irq_save(flags);
+
+ /* Disable interrupt in EPIT module */
+ epit_irq_disable(epittm);
+
+ /* Clear pending interrupt, only while switching mode */
+ if (!clockevent_state_oneshot(ced))
+ epit_irq_acknowledge(epittm);
+
+ /*
+ * Do not put overhead of interrupt enable/disable into
+ * epit_set_next_event(), the core has about 4 minutes
+ * to call epit_set_next_event() or shutdown clock after
+ * mode switching
+ */
+ epit_irq_enable(epittm);
+ local_irq_restore(flags);
+
+ return 0;
+}
+
+static irqreturn_t epit_timer_interrupt(int irq, void *dev_id)
+{
+ struct clock_event_device *ced = dev_id;
+ struct epit_timer *epittm = to_epit_timer(ced);
+
+ epit_irq_acknowledge(epittm);
+
+ ced->event_handler(ced);
+
+ return IRQ_HANDLED;
+}
+
+static int __init epit_clockevent_init(struct epit_timer *epittm)
+{
+ struct clock_event_device *ced = &epittm->ced;
+ struct irqaction *act = &epittm->act;
+
+ ced->name = "epit";
+ ced->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_DYNIRQ;
+ ced->set_state_shutdown = epit_shutdown;
+ ced->tick_resume = epit_shutdown;
+ ced->set_state_oneshot = epit_set_oneshot;
+ ced->set_next_event = epit_set_next_event;
+ ced->rating = 200;
+ ced->cpumask = cpumask_of(0);
+ ced->irq = epittm->irq;
+ clockevents_config_and_register(ced, clk_get_rate(epittm->clk_per),
+ 0xff, 0xfffffffe);
+
+ act->name = "i.MX EPIT Timer Tick",
+ act->flags = IRQF_TIMER | IRQF_IRQPOLL;
+ act->handler = epit_timer_interrupt;
+ act->dev_id = ced;
+
+ /* Make irqs happen */
+ return setup_irq(epittm->irq, act);
+}
+
+static int __init epit_timer_init(struct device_node *np)
+{
+ struct epit_timer *epittm;
+ struct clk *clk_ipg;
+ int ret;
+
+ epittm = kzalloc(sizeof(*epittm), GFP_KERNEL);
+ if (!epittm)
+ return -ENOMEM;
+
+ epittm->base = of_iomap(np, 0);
+ if (!epittm->base) {
+ ret = -ENXIO;
+ goto out_kfree;
+ }
+
+ epittm->irq = irq_of_parse_and_map(np, 0);
+ if (!epittm->irq) {
+ ret = -EINVAL;
+ goto out_kfree;
+ }
+
+ clk_ipg = of_clk_get_by_name(np, "ipg");
+ if (IS_ERR(clk_ipg)) {
+ pr_err("i.MX EPIT: unable to get clk_ipg\n");
+ ret = PTR_ERR(clk_ipg);
+ goto out_kfree;
+ }
+ clk_prepare_enable(clk_ipg);
+
+ epittm->clk_per = of_clk_get_by_name(np, "per");
+ if (IS_ERR(epittm->clk_per)) {
+ pr_err("i.MX EPIT: unable to get clk_per\n");
+ ret = PTR_ERR(epittm->clk_per);
+ goto out_clk_ipg_disable;
+ }
+ clk_prepare_enable(epittm->clk_per);
+
+ /*
+ * Initialise to a known state (all timers off, and timing reset)
+ */
+ writel_relaxed(0x0, epittm->base + EPITCR);
+ writel_relaxed(0xffffffff, epittm->base + EPITLR);
+ writel_relaxed(EPITCR_EN | EPITCR_CLKSRC_REF_HIGH | EPITCR_WAITEN,
+ epittm->base + EPITCR);
+
+ ret = epit_clocksource_init(epittm);
+ if(ret) {
+ pr_err("i.MX EPIT: failed to init clocksource\n");
+ goto out_clk_per_disable;
+ }
+
+ ret = epit_clockevent_init(epittm);
+ if(ret) {
+ pr_err("i.MX EPIT: failed to init clockevent\n");
+ goto out_clk_per_disable;
+ }
+
+ return 0;
+
+out_clk_per_disable:
+ clk_disable_unprepare(epittm->clk_per);
+out_clk_ipg_disable:
+ clk_disable_unprepare(clk_ipg);
+out_kfree:
+ kfree(epittm);
+
+ return ret;
+}
+TIMER_OF_DECLARE(mx6q_timer, "fsl,imx6q-epit", epit_timer_init);
--
2.17.0
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